Tom Sawyer and Huck Finn also appear in at least three unfinished Twain works, Huck Finn and Tom Sawyer Among the Indians (a sequel to Huckleberry Finn), Schoolhouse Hill (a version of The Mysterious Stranger) and Tom Sawyer's Conspiracy (a sequel to Tom Sawyer, Detective). While all three, uncompleted works had been posthumously published, only Tom Sawyer's Conspiracy displays a complete plot and nearly complete story. Twain abandoned the other two works after only finishing a few chapters.

Thomas "Tom" Sawyer is based on the young Samuel Clemens is a cunning and playful boy of about twelve years of age, and the protagonist of the story. His best friends include Joe Harper and Huckleberry Finn. He has a half-brother, Sid, a cousin, Mary, and an Aunt Polly, the sister of his and Sid's dead mother. He lives with them in the town of St. Petersburg, Missouri. In addition, he has another aunt, Sally Phelps, who lives considerably farther down the Mississippi River, in the town of Pikesville. Tom loves to go on adventures and wants to become an Indian pirate. He falls in love with his classmate Becky Thatcher, and was once "engaged" to Amy Lawrence. Tom is imaginative and obsessed with stories.

Mary is Tom's "saintly" cousin. She helps Tom memorize his Bible verses, and has memorized enough herself to receive two Bible prizes in Sunday school. Even when Tom's at his most incorrigible, she can usually find something nice to say on his behalf. She's the antidote to Tom's poisonously annoying brother Sid.

Mary's mother and Tom and Sid's aunt, the sister of their dead mother. Tom and Sid live with Aunt Polly and her daughter Mary. Despite the relentless discipline and spiritual guidance she dispenses, she comes off as a caring, noble character. When Tom points out that nobody seems to care about Huck's being alive after they were both presumed dead, Aunt Polly generously gives her love to Huck as well -"And so they shall. I'm glad to see him, poor motherless thing!" and the loving attentions Aunt Polly lavished upon him were the one thing capable of making him more uncomfortable than he was before". In fact, the last impression we get of Aunt Polly is of a similar nature - "There was something about aunt Polly's manner, when she kissed Tom, that swept away his low spirits and made him light hearted and happy again".

Tom's whiny half-brother, who also lives with Aunt Polly and Mary. He behaves well but enjoys getting Tom into trouble and tattles on Tom. He appears to be around nine years old, and lies; he also seems to annoy Tom frequently. He is always on Aunt Polly's "good side" while Tom is on Aunt Polly's "bad side".

Huck's abusive, drunken father and the main antagonist of Adventures of Huckleberry Finn. He had vanished but shows up at the beginning of the story and forcibly takes his son to live with him. He also tries to sue Judge Thatcher to get the six thousand dollars Huck had given the Judge for safekeeping and confiscates whatever money Huck has in his pocket, using it to get drunk. He is infuriated that his son would try to amount to more than he did and live in better conditions. He demands that Huck quit school, threatening him with whipping. Soon after Huck escapes, Pap Finn leaves to search for him and doesn't return. At the end of the book, Jim reveals to Huck: the corpse they found in the abandoned house early in the book was actually that of Huck's father. Pap Finn's backstory is explored in Finn: A Novel (2007), by Jon Clinch.[1]

Joseph "Joe" Harper is Tom's friend; he joins Tom and Huck as a pirate when they run away from home to Jacksons Island. He does not appear in The Adventures of Tom Sawyer other than on this adventure. His mother is Sereny Harper and his sisters are Susan and Faith.

Injun Joe is the main antagonist of The Adventures of Tom Sawyer and is feared by the town. He is a half Native American, half white man who was whipped by Mr. Douglas, a police officer. After Tom Sawyer witnesses the murder of Doctor Robinson and the framing of Muff Potter, Huck Finn overhears Injun Joe plotting the mutilation of Widow Douglas. Towards the end of the book, Tom sees Injun Joe inside the cave, but Injun Joe is unable to see Tom's face. At the end of the book, Injun Joe is found dead behind the newly sealed cave entrance.

Jim flees slavery with Huck, who was escaping his drunken father, but he may have chosen to accompany Huck out of mere boredom. Jim hopes to reach the free states and buy his family's freedom. At the end of the book, Tom reveals that his owner had died since they left home, and she had freed Jim in her will. Of Jim, Russell Baker wrote:

"The people whom Huck and Nigger Jim encounter on the Mississippi are drunkards, murderers, bullies, swindlers, lynchers, thieves, liars, mows, frauds, child abusers, numbskulls, hypocrites, windbags and traders in human flesh. All are white. The one man of honor in this phantasmagoria is 'Nigger Jim,' as Twain called him to emphasize the irony of a society in which the only true gentleman was held beneath contempt."[2]

(The words "nigger" and "Jim" appear side-by-side only once in Adventures of Huckleberry Finn, in Chapter XXXI, in a letter Huck writes to Mrs. Watson, but they are not used as a name. After "nigger Jim" appeared in Albert Bigelow Paine's 1912 Clemens biography, it continued to be used by twentieth-century critics, including Leslie Fiedler, Norman Mailer, Ernest Hemingway, and Russell Baker.)[citation needed]

Two con men whom Huck meets in his adventures down the Mississippi. They join Huck and Jim on the raft to escape an angry mob that was chasing them out of a town. The younger one initially claims to be the true heir of the Duke of Bridgewater, and the older one the lost son of Louis XVI and the rightful king of France. Thus, Huck refers to them as "the king" and "the duke" throughout the narration of the book. During their time in the story, they collaborate to stage many shenanigans, including pretending to be the brothers of a deceased man so they can steal the money left to them in the will. They are later separated from Huck and Jim, tarred and feathered, and ridden out of town on a rail.

Amy is Becky Thatcher's rival for most of The Adventures of Tom Sawyer, and dislikes Becky. Amy is Tom's first love, but is swept from his thoughts the moment he sees Becky. After a little slipup from Tom he returns to Amy to make Becky jealous.

Muffren "Muff" Potter is a drunk fisherman who loves children and is a close friend of Tom's. He often mends the children's kites and helps them fish. Muff Potter is falsely accused of murdering Dr. Robinson in the beginning of the story. In fact, Injun Joe killed the Doctor and managed to convince Muff that Muff committed the murder. Tom saves Muff's life, while endangering his own, by telling the truth about the Robinson murder.

The doctor who wanted the grave dug up. He was subsequently murdered by Injun Joe, who framed Muff Potter for the crime.

A different character of the same name in Adventures of Huckleberry Finn was the only man who recognized that the King and Duke were phonies when they tried to pretend to be British. He warned the townspeople, but they ignored him.

Becky is Judge Thatcher's daughter, known for her love interest with Tom Sawyer. Her long blonde hair is always worn in braids. She wins Tom's love from the first moment he sees her. When Becky first encounters Tom, she gives him a purple pansy to show her love. Becky Thatcher soon becomes "engaged" to Tom Sawyer by swearing to love only him and sealing their engagement with a kiss on the lips. When Tom mentions that he used to be with Amy Lawrence, Becky believes Tom still loves Amy and gets angry at him. Tom wins her back by telling a lie and takes the whipping for the vandalism of their teacher's anatomy book, which Becky accidentally ripped. In "Huckleberry Finn", she is also referred to as "Bessie".[3] The character Becky was based on Laura Hawkins, an actual friend of Samuel Clemens.[4]

Although Judge Thatcher, Becky Thatcher's father, plays a minor role in The Adventures of Tom Sawyer, he plays a substantial role in "The Adventures of Huckleberry Finn". Judge Thatcher shares responsibility for Huckleberry Finn with Widow Douglas, and it is to Judge Thatcher that Huckleberry Finn signs over his fortune in order to keep it from his father.